[IRCA] "Airport-Friendly" FSL Antenna Designs

[d1028gary@xxxxxxxxxxx]

Up until very recently it was only a dream to be able to enjoy high-sensitivity MW-DXing in a motel room after long distance air travel. Ultralight radios (hot-rodded and stock) could be packed away for some basic DXing fun, but serious high-gain antennas required either serious packing space, or deployment outside of the motel room (a dubious possibility in most cases). 

In an effort to make high gain MW-DXing possible during long range air travel, a new series of "Frequent Flyer" FSL antennas was developed here over the winter. These antennas were designed to be serious MW-DXing performers, but still have non-subversive appearances, allowing them to routinely pass through TSA security screening at major airports. All of them can easily be carried within standard hand-carry luggage (while protected by matched-sized plastic totes). Because of the increased MW-band sensitivity provided by the new 1162/46 Litz wire, it was possible to shrink the size of the 2012-year 5" Mini-FSL model (providing inductive coupling gain roughly equivalent to that of a 4' air core box loop, fully described at http://www.mediafire.com/file/9ze98h293s85p86/5_inch_FSL.doc 
down to a very compact size, allowing the development of this "Frequent Flyer" FSL series. 

Three new "Frequent Flyer" FSL designs have been built and tested, and two recent Hawaii DXpeditions were conducted with the first of these models. The 5" Bar FSL model (design photo at https://app.box.com/s/2lixzaly97goivq7i3qqj6etrr0ce109 ) was used by Craig Barnes for a very successful trip to Princeville, Kauai (during which about 40 Asian TP's were received on a stock Tecsun PL-310 model), and I had a very enjoyable DXing trip to Kona on the Big Island, receiving exotic Pacific Island DX at S9 levels (fully described at http://swling.com/blog/tag/gary-debock/ This model has successfully passed through airport TSA screening checkpoints 7 times, although the 100mm Russian surplus ferrite bars used in its construction are extremely scare, limiting the number of these models that can be made (only 5 are planned). Performance-wise, through, the following ferrite bar model can provide equivalent MW sensitivity with readily available construction parts. 

The new 3.5" ferrite bar model (design photo at https://app.box.com/s/az7wz583mpgeftw98v04zah7nc9nj4z0 ) was designed to combine high performance with easy construction, and readily available parts. It has a smaller diameter than the above FSL model but longer ferrite length, giving it equivalent MW sensitivity. The 27 Russian surplus 160mm x 8mm ferrite rods can be purchased on eBay for about $70 shipped, giving the model an overall construction cost of about $150 US. It uses the same high-sensitivity 1162/46 Litz wire as the above FSL model, but because of the ferrite rod design it can provide inductive coupling boosts on both the sides of the antenna, as well as in the front or back. A full "Heathkit-like" construction article is planned for this model, similar to the 2012 5" Mini-FSL model article linked above. 

Finally a "economy-class" 4.7" Frequent Flyer model using the commonly-available Russian surplus 62mm ferrite bars has also been built, with the design photo at https://app.box.com/s/mlnhho99rswvdrp62ik634ft7t5a6s9a . This model can be built for around $65 US, and provides a good inductive coupling boost to a stock Ultralight radio (with greater MW sensitivity than the 7.5" loopstick hot-rodded models). Because of the limited ferrite bar length their isn't enough space to wind the required number of 1162/46 Litz wire coil turns on this model, so 660/46 Litz wire is used instead. That is one of the reasons why the construction cost of this model is significantly lower, since 660/46 is relatively cheap by comparison. Thomas Witherspoon of SWLing.com was kind enough to post an article detailing the runoff of this "economy class" FSL model against the Terk Advantage commercial loop, at http://swling.com/blog/2017/03/daytime-dx-gary-compares-terk-advantage-with-homebrew-fsl-loop/ Depending upon interest in this FSL model, a full-construction article may also be written in the future. 

Hopefully these compact, high performance FSL antennas will give DXers some new options for enjoying their hobby during long-range air travel. 

73 and Good DX, 
Gary DeBock (in Puyallup, WA, USA) 
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